Over-current protection for electrical loads is common place. To this end, transistor based current limiting circuits are well known.
In one such circuit, a transistor is used as a switch to switch current to a load. In the presence of a sensed over-current condition, a further transistor switch is turned on, in order to turn off the load current switching transistor. As explained below, as the load impedance, the voltage across the load current switching transistor increases in order to maintain a constant current. This requires the load current switching transistor to dissipate a large amount of power, which in turn, requires the load current switching transistor to have a high power rating and/or to be prone to failure.
Accordingly, there remains a need for a current limiting transistor circuit that requires the current switching transistor to dissipate less power.